1. Field of the Invention
The present invention relates to a fingerprint recognition device, and more particularly, to a fingerprint authentication device which can be inserted into a card to authenticate a card user.
2. Description of the Related Art
As information technologies have been developed and e-commerce grows, there is an increasing need for accurate user authentication. In order for a machine to identify a person, identifications (IDs), passwords, resident registration numbers, names, and the like are widely used. Currently, biometrics has been widely applied. However, information such as the IDs, passwords, resident registration numbers, and the like can be exposed in real life easily stolen. Therefore, it is concluded that a bodily feature which is determined as the most difficult thing to be reproduced is the most reliable authentication means in the information age.
A fingerprint forms ridges with sweat glands. Fingerprints differ and do not change through life. This is why a fingerprint is printed onto a resident registration card. A fingerprint authentication system refers to a technology for identifying and authenticating a person using a fingerprint that the person has from birth through a fingerprint recognition device or system, and the fingerprint authentication system has a very high security. The fingerprint authentication system is applied to biometrics and can be implemented at low cost as compared with other authentication systems using other body portions excluding the fingerprint, so that the fingerprint authentication system has been widely used for identification and authentication technologies.
The fingerprint recognition device or the fingerprint recognition system that has been widely used in people's lives includes 2D fingerprint recognition and 3D fingerprint recognition. The 2D fingerprint recognition is generally used and can be implemented at very low cost. However, there is a problem in that the authentication can be performed by only using a picture of a fingerprint. The 3D fingerprint authentication further uses depths of a valley and a ridge of a fingerprint as a recognition factor and has high accuracy.
A first step of fingerprint recognition is capturing a fingerprint. In order to sense a shape of the fingerprint, a pressure sensor or an optical image sensor is generally used.
FIG. 1 illustrates a conventional pressure sensor used to sense a shape of a fingerprint.
Referring to FIG. 1, a pressure sensor 100 includes a plurality of pixels 110 provided to touch a finger having a fingerprint to be recognized, a plurality of capacitors 120 having terminals connected to the respective pixels 110, and a sense circuit 130 connected to the other terminals of the plurality of capacitors 120. Pressures exerted on a plurality of the pixels 110 are different according to depths of a valley and a ridge of a fingerprint. According to touch pressures, capacitances of the capacitors 120 corresponding to the pixels 110 are changed. The sense circuit 130 connected to the other terminals of the plurality of the capacitors 120 scans changes in a capacitance of a corresponding capacitor 120 and generates a shape of a fingerprint touching the fingerprint recognition device 100 as data.
The pressure sensor 100 illustrated in FIG. 1 has advances of a small size and low manufacturing costs. However, when a finger touches the pressure sensor 100, pressures exerted on the pressure sensor 100 from the finger even by the same person differ whenever touching the pressure sensor. Particularly, in order to consider too strong or too weak pressures, a proper area of a pixel and a capacitance of a corresponding capacitor have to be controlled. Since controlling the area of the pixel and the capacitance of the corresponding capacitor in consideration of the aforementioned situations is technologically difficult, a fingerprint recognition performance of the pressure sensor 100 that has been currently used is not good.
FIG. 2 illustrates a conventional optical image sensor used to sense a shape of a fingerprint.
Referring to FIG. 2, the optical image sensor 200 includes a silicon touch unit 210, a condenser lens 220, and an image sensor 230. The silicon touch unit 210 is implemented by using a material that remembers a shape according to depths of a valley and a ridge of a fingerprint for a predetermined time after the fingerprint leaves the silicon touch units 210. The condenser lens 220 transmits a reflected wave that is a light incident onto the remembered shape of the fingerprint and reflects to the image sensor 230. A resolution of the fingerprint recognized through the optical image sensor 200 illustrated in FIG. 2 is very higher than that of a fingerprint recognized by using the pressure sensor 100 illustrated in FIG. 1. However, as it can be seen through vertical structures illustrated in FIGS. 1 and 2, a size of the optical image sensor 200 illustrated in FIG. 2 is very large and manufacturing costs consumed to implement the optical image sensor 200 are relatively high.
A credit card that has been widely used authenticates an ID of a card user through a password. In this case, the password has to be stored by a bank or a credit information company, and this information always has a possibility of leakage. Therefore, if there is a credit card having the aforementioned fingerprint recognition function, without using a password that can be leaked and so the user may be damaged, the ID of the card user can be checked.
In order to realize the method, the credit card having the fingerprint recognition function is needed. However, the pressure sensor illustrated in FIG. 1 has a problem with the fingerprint recognition performance, and the optical image sensor illustrated in FIG. 2 has a large size and cannot be inserted into the credit card.